Hydrological Dynamics in Various Agroecological Zones and Impacts of Soil and Water Conservation Measures on Runoff and Sediment Yield in the Africa ecoregion, Bale Eco- Region

Abstract

<title>Abstract</title> Protecting and conserving Africa's ecoregions is crucial for mitigating environmental challenges, maintaining the continent's ecological health, ensuring the survival of its unique species, and supporting the livelihoods of its people. The Bale Eco-Region (BER) of Southern Ethiopia is characterized by high surface runoff and sediment yield. This study assessed hydrological dynamics across different agro-ecological systems and rainfall pattern in three watersheds (Bekaye, Hawo and Horosoba) for the period 2016-2023. It also investigated the impacts of soil and water conservation (SWC) measures on runoff and sediment yield for Bekaye watershed that has different rainfall pattern from most of previous study in the country. Data on rainfall, water level, and suspended sediment concentrations were collected from 2016 to 2023. Significant differences in runoff coefficient and sediment yield were observed among the watersheds. Bekaye experienced more intense rainfall events compared to Hawo and Horosoba. Bekaye had a higher runoff coefficient (38.4%) and sediment yield (15.5 t/ha) while Hawo had lower runoff coefficient (19.6%) and sediment yield (3.2 t ha⁻¹ yr⁻¹). The volume of runoff and suspended sediment concentration were measured for the Bekaye watershed before (2016) and after SWC interventions (2017-2023). The SWC interventions in Bekaye help in reducing runoff and sediment yield, as well as increasing base flow in the subsequent years. The results of this research, conducted under different rainfall patterns, show a lower reduction in sediment yield (&lt;30%) compared to most earlier studies that reported a reduction of more than 40%. Thus, conducting comparative studies across different regions with varied rainfall patterns and catchment characteristics is crucial to identifying the key factors influencing sediment yield. Generally, long-term monitoring and maintenance are key to ensuring that SWC measures continue to provide benefits in diverse agroecological settings.